Gear product and method for manufacturing the same

ABSTRACT

In a gear product, a plurality of tooth having a crowning formed in a pattern unified to one pattern selected from fourteen patterns comprising four patterns in which a crowning is formed at one of an upper end part A or lower end part B of an upper inclined surface  91 , an upper end part C or a lower end part D of a lower inclined surface  92 , six patterns in which crownings are formed at two parts thereof and four patterns in which crownings are formed with three parts thereof, are formed at an equal pitch on an outer peripheral surface of a gear part. In a helical gear  9 , a combination pattern of an upper part A of an upper side tooth surface  91  and a lower part D of a lower tooth surface  92  or a pair of an upper part C of the lower tooth surface  92  and a lower part D of the upper tooth surface  92  is formed by forging device.

TECHNICAL FIELD

The present invention relates to a gear product (including a gear withmissing teeth) having a plurality of tooth formed at a predeterminedpitch on an outer peripheral surface of a disc-form part thereof.

BACKGROUND ART

Crowning F,F,F,F are formed at four parts of every both end parts oftooth surfaces of tooth form of a gear product so that tooth thicknessmay gradually decrease from the center part thereof toward both ends oftooth, as shown in FIG. 9 and tooth surfaces engaging each other mayalways maintain the point contact thereof. A gear product with crowningwas manufactured by forming a product having a tooth form withoutcrowning by cutting or forging, and cutting four end parts of toothsurfaces of every tooth so as to form crowning.

In the step of forming crownings at four parts of every tooth bycutting, there were problems that it took a lot of time and trouble, thedispersion of accuracy due to the abrasion of tools and the wastage costof tools could not be ignored.

In consideration of a purpose of a crowning, there is no problem infunction of the crowning as long as crownings are formed on any one oftooth surfaces engaging each other.

Making it possible to produce crownings by forging would be able toenhance efficiency greatly and lower costs.

DISCLOSURE OF THE INVENTION

It is an object of the present invention to provide a gear product and amethod for manufacturing the same, in which by forming a crowning on anyone of tooth surfaces engaging each other, it is able to reduce thetrouble of process for forming a crowning, to abbreviate machining time,to reduce the dispersion of accuracy due to the abrasion of tools andthe wastage cost of tools, to enhance efficiency greatly, and to lowercosts.

It is another object of the present invention to reduce a machining timefor forming a crowning and to provide a technology for forming acrowning by forging.

The present invention is based on a technical concept that in a gearproduct having plurality of tooth formed at a predetermined pitch on anouter peripheral surface of a disc-form body thereof, a crowning isformed at least at one end part of a tooth surface of at least one ofgears engaging each other.

The present invention (the first invention described in claim 1)provides a gear product having a plurality of tooth profiles formed at apredetermined pitch on an outer peripheral surface of a disc-form bodythereof, in which a crowning is formed at least at one end part of atooth surface of at least one of gears engaging each other.

The present invention (the second invention described in claim 2),according to the first invention, provides a gear product in which thecrowning is formed at least at one end part of an upper side toothsurface or a lower side tooth surface of at least one or the other gear.

The present invention (the third invention described in claim 3),according to the first invention, provides a gear product in which thecrowning is formed at two end parts arbitrarily selected from four endparts of both of an upper side tooth surface and a lower side toothsurface of one or the other gear.

The present invention (the fourth invention described in claim 4),according to the first invention, provides a gear product in which thecrowning is formed at three end parts arbitrarily selected from four endparts of both of an upper side tooth surface and a lower side toothsurface of one or the other gear.

The present invention (the fifth invention described in claim 5),according to the first invention, provides a gear product in which thecrowning is formed at an upper end part of an upper side tooth surfaceof one gear and the crowning is formed at the upper end part and a lowerend part of the upper side tooth surface and a lower end part of a lowerside tooth surface of the other gear.

The present invention (the sixth invention described in claim 6),according to the first invention, provides a gear product in which thecrowning is formed at upper and lower end parts of an upper side toothsurface and an upper end part of a lower side tooth surface of one gear,and the crowning is formed at the upper and lower end parts of the upperside tooth surface and a lower end part of the lower side tooth surfaceof the other gear.

The present invention (the seventh invention described in claim 7),according to the first invention, provides a gear product in which thecrowning is formed at an upper end part of an upper side tooth surfaceand a lower end part of a lower side tooth surface of one gear.

The present invention (the eighth invention described in claim 8),according to the first invention, provides a gear product in which thecrowning is formed at upper and lower end parts of an upper side toothsurface and a lower end part of a lower side tooth surface of one gearand the crowning is formed at the upper end part of the upper side toothsurface and the lower end part of the lower side tooth surface of theother gear.

The present invention (the ninth invention described in claim 9),according to the first invention, provides a gear product in which thecrowning is formed at a lower end part of an upper side tooth surfaceand an upper end part of a lower side tooth surface of one gear.

The present invention (the tenth invention described in claim 10),according to the first invention, provides a gear product in which thecrowning is formed at a lower end part of an upper side tooth surfaceand an upper end part of a lower side tooth surface of one gear and thecrowning is formed at the lower end part of the upper side tooth surfaceand the upper end part of the lower side tooth surface of the othergear.

The present invention (the eleventh invention described in claim 11)provides a technology which enables to reduce machining time for forminga crowning and a technology for forming a crowning by the utilization offorging means, and provides a gear product having a plurality of toothformed at a predetermined pitch on an outer peripheral surface of adisc-form body thereof, in which tooth forms of all teeth are unified toone pattern selected from a plurality of pattern in which a crowning isformed at at least one of four parts of every both ends on each toothsurface of the teeth and the crowning is not formed at the other of thefour parts thereof.

The present invention (the twelfth invention described in claim 12),according to the eleventh invention, provides a gear product in whichthe selected pattern is one of fourteen patterns comprising fourpatterns in which the crowning is formed at one of an upper end part orlower end part of a upper inclined surface, and an upper end part or alower end part of a lower inclined surface, six patterns in which thecrownings are formed at two parts such as the upper end part and thelower end part of the upper inclined surface, the upper end part of theupper inclined surface and the upper end part of the lower inclinedsurface, the upper end part of the upper inclined surface and the lowerend part of the lower inclined surface, the lower end part of the upperinclined surface and the upper end part of the lower inclined surface,the lower end part of the upper inclined surface and the lower end partof the lower inclined surface, or the upper end part and lower end partof the lower inclined surface, and four patterns in which the crowningsare formed at three parts such as the upper end part and the lower endpart of the upper inclined surface and the upper end part of the lowerinclined surface, the upper end part and the lower end part of the upperinclined surface and the lower end part of the lower inclined surface,the upper end part of the upper inclined surface and the upper end partand the lower end part of the lower inclined surface, or the lower endpart of the upper inclined surface and the upper end part and the lowerend part of the lower inclined surface.

The present invention (the thirteenth invention described in claim 13),according to any one of the inventions from the first to the twelfth,provides a gear product in which the plurality of tooth formed on theouter peripheral surface of the disc-form part thereof is a helicaltooth.

The present invention (the fourteenth invention described in claim 14)provides a method for manufacturing a gear product having a plurality oftooth formed at a predetermined pitch on an outer peripheral surface ofa disc-form body thereof, in which a crowning is formed at least at oneend part of tooth surface of at least one of gears engaging each other.

The present invention (the fifteenth invention described in claim 15),according to the fourteenth invention, provides a method formanufacturing a gear product in which a tooth form having the crowningof a tooth formed on the outer peripheral surface is formed by cutting.

The present invention (the sixteenth invention described in claim 16),according to the fourteenth invention, provides a method formanufacturing a gear product in which a tooth form having the crowningof a helical tooth formed on the outer peripheral surface is formed byupsetting on forging.

The present invention (the seventeenth invention described in claim 17),according to the fourteenth invention, provides a method formanufacturing a gear product in which a tooth form having the crowningof a helical tooth formed on the outer peripheral surface is formed byironing on forging.

The present invention (the eighteenth invention described in claim 18)provides a method for manufacturing a gear product in which a firstmolding having a plurality of tooth, having no crowning, formed at apredetermined pitch on an outer peripheral surface of a disc-form bodythereof is cut so that tooth forms of all teeth may be unified to apattern selected from a plurality of pattern in which the crowning isformed at at least one of four parts of every both ends on each toothsurface of the teeth and the crowning is not formed at the other of thefour parts thereof.

The present invention (the nineteenth invention described in claim 19)provides a method for manufacturing a gear product in which a firstmolding having a plurality of helical tooth, having no crowning, formedat a predetermined pitch on an outer peripheral surface of a disc-formbody thereof is molded by upsetting so that the crowning can be formedat an upper part of an upper side tooth surface and a lower part of alower side tooth surface among four parts of both ends parts of toothsurfaces of the all teeth.

The present invention (the twentieth invention described in claim 20)provides a method for manufacturing a gear product in which a firstmolding having a plurality of helical tooth, having no crowning, formedat a predetermined pitch on an outer peripheral surface of a disc-formbody thereof is molded by ironing so that the crowning may be formed ata lower part of an upper side tooth surface and an upper part of a lowerside tooth surface among four parts of both end parts of tooth surfacesof the all teeth.

The present invention achieves rationalization by decreasing at leastone cutting part in case that the crowning is formed by cutting.

Moreover, in case that the crowning is formed by forging, the presentinvention has an advantage that there is no need of cutting, it isefficient and there is no dispersion.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an explanation diagram showing a step for forming the firstmolded article in the manufacturing method according to the presentinvention;

FIG. 2 is an explanation diagram showing the first molded article;

FIG. 3 is an explanation diagram showing patterns of a crowning formedby cutting process;

FIG. 4 is an explanation diagram showing examples of gears engaging eachother;

FIG. 5 is an explanation diagram showing an example of forming crowningsin upsetting process;

FIG. 6 is an explanation diagram showing a combination of gears formedin upsetting process;

FIG. 7 is an explanation diagram showing an example of forming acrowning in ironing process;

FIG. 8 is an explanation diagram showing a combination of gears formedin ironing process; and

FIG. 9 is an explanation diagram showing a conventional pattern offorming crownings.

BEST MODE FOR CARRYING OUT THE INVENTION

A gear product and a method for manufacturing the same according to thepresent invention will now be described with reference to the drawings.

FIG. 1 shows a forming step of the first molded article. In FIG. 1, 1 isa cope, 2 is a drag and a mandrel 3 is projected at the center of apressure surface of the cope 1.

Meanwhile, a cavity 4, which is two-stage form composed of a disc-formlike boss forming part 4 a for forming a boss and a disc-form gearforming part 4 b for forming a gear, is provided in the drag 2. A toothform or profile 5 for forming helical gear is formed on an innerperipheral surface corresponding to the gear forming part 4 b and aknockout sleeve 6 is provided on a bottom surface so as to projectmovably.

When a disc-form work W set at an opening of the cavity 4 is depressedby the cope 1 (as shown in FIG. 1(b)), the work W is compressed into thecavity 4, the cavity 4 is filled with the work W, a boss part 7 isformed at the bottom surface by extrusion and a helical tooth 9 isformed on an outer peripheral surface of a disc-form gear part 8 havingan axial hole.

When the cope 1 is send up so as to release the pressure, a first moldedarticle W1 shown in FIG. 2 can be took out by push up of the knockoutsleeve 6.

The helical tooth 9 of the first molded article W1 molded in thisprocess has no crowning.

Then, a crowning is formed in the second process.

There are three methods for forming a crowning. In the first, one ofthem is a cutting process.

The cutting process is the same as a conventional cutting process withcutting tools.

However, cut parts are not all of the four parts of both end parts ontooth surfaces and a crowning is formed in one pattern selected fromfourteen patterns. The fourteen patterns comprise four patterns in whichthe crowning is formed at one of an upper end part A or a lower end partB of an upper inclined surface 91, an upper end part C or a lower endpart D of a lower inclined surface 92 (as shown in FIG. 3(a)); sixpatterns in which crownings are formed at two parts such as the upperend part A and the lower end part B of the upper inclined surface 91,the upper end part A of the upper inclined surface 91 and the upper endpart C of the lower inclined surface 92, the upper end part A of theupper inclined surface 91 and the lower end part D of the lower inclinedsurface 92, the lower end part B of the upper inclined surface 91 andthe upper end part C of the lower inclined surface 92, the lower endpart B of the upper inclined surface 91 and the lower end part D of thelower inclined surface 92, or the upper end part C and the lower endpart D of the lower inclined surface 92 (as shown in FIG. 3(b)); andfour patterns in which crownings are formed at three parts such as theupper end part A and the lower end part B of the upper inclined surface91 and the upper end part C of the lower inclined surface 92, the upperend part A and the lower end part B of the upper inclined surface 91 andthe lower end part D of the lower inclined surface 92, the upper endpart A of the upper inclined surface 91 and the upper end part C and thelower end part D of the lower inclined surface 92, or the lower end partB of the upper inclined surface 91 and the upper end part C and thelower end part D of the lower inclined surface 92 (as shown in FIG.3(c)).

In the gear products formed in the above described manner, there is noproblem in function of a crowning as long as a crowning is formed on atleast one tooth surface of gears engaging each other such as a gear Phaving a crowning formed at the upper end part A of the upper inclinedsurface 91 and a gear Q having crownings formed at the lower end part Bof the lower inclined surface 92 and the upper end part C and lower endpart D of the upper inclined surface 91 (since a inclination of a toothon the gear Q is reverse relation to that of a tooth on the gear P andthe upper inclined surface 91 of the gear P is engaged with the lowerinclined surface 92 of the gear Q, the responding symbol is used to theengaged part of the gear Q which is engaged with that of the gear G), asshown in FIG. 4(a).

Moreover, for example, in the combination of a gear R on which crowningsare formed at the upper end part A and the lower end part B of the upperinclined surface 91 and the upper end part C of the lower inclinedsurface 92, and a gear S on which crownings are formed at the lower endpart B of the lower inclined surface 92 and the upper end part C and thelower end part D of the upper inclined surface 91 (as shown in FIG.4(b)), there is no problem when crownings are redundantly formed at thecorresponding parts respectively such as the lower end part B of theupper inclined surface 91 and the upper end part C of the lower inclinedsurface 92 on the gear R and the lower end part B of the lower inclinedsurface 92 and the upper end part C of the upper inclined surface 91 onthe gear S. It is proper that the crowning is formed on at least onepart of engaged part for engaging the other on the combination of gears.

In the second method of the three methods for manufacturing a crowning,a crowning is formed by upsetting process as a forging process, In thisupsetting process, as shown in FIG. 5(a) and FIG. 5(b), a helical tooth9 is depressed in an axial direction in a die 10 for forming a helicaltooth. When the helical tooth 9 is depressed, a lower part of an upperside surface 91 and an upper part of a lower side surface 92 arestrongly depressed on an inner surface of the die 10 for forming ahelical tooth.

Meanwhile, an upper part of the upper side tooth surface 91 and a lowerpart of the lower side tooth surface 92 are weakly depressed and theupper part of the upper side tooth surface 91 and a lower part of thelower side tooth surface 92 are stretched toward inside thereof.

Therefore, crownings are formed at the upper part A of the upper sidetooth surface 111 and the lower part D of the lower side tooth surface112 of a helical tooth 11 of the gear shown in FIG. 5(b) and the gear Tshown in FIG. 6.

In this way, crownings formed by upsetting process are formed at partshaving left-to-right inverted relationship determined by an inclineddirection of a helical tooth. Therefore, in a pair of the gear T and agear U having crownings formed in reverse patterns with each other,crownings are formed at all of four parts A,B,C,D of a meshing surfaceof any teeth.

In the ironing process as one of remaining forging processes, a helicaltooth 9 is ironed along a tooth trace by putting the helical tooth 9through a die 13 for forming a helical tooth having constrictions formedon an inner surface thereof, as shown in FIGS. 7(a)-(c).

Crownings F,F are formed at a lower part of an upper side tooth surface141 and the upper part of the lower side tooth surface 142 of a helicaltooth 14 by ironing.

In this way, crownings formed by ironing process also are formed atparts having left-to-right inverted relationship determined by aninclined direction of a helical tooth. Therefore, in a pair of the gearV and a gear W having crownings formed in reverse patterns with eachother, crownings are formed at all four parts A,B,C,D of a meshingsurface of any teeth.

When the crowning is formed in upsetting and ironing process as one offorging processes, there is no need of cutting process, the crowning isformed instantly and there is no dispersion.

By the way, in a case that a crowning is formed by cutting, crowningscan be formed at any other tooth form except for a helical tooth.

Moreover, there is no problem in finishing a crowning formed by forgingprocess so as to raise the accuracy of the crowning.

In all gear products manufactured by these forging processes, when onecrowning of both side tooth surface in tooth trace direction is formedat an upper end part of one side tooth surface, the other crowningthereof is formed at an lower end part of the other side tooth surface.Meanwhile, on cutting process, the crownings can be formed on allpatterns shown in FIG. 3 and in result, the number of the cut parts isless than the number of cut parts in a conventional cutting process.

Moreover, it is able to achieve rationalization by the combination offorging and cutting.

The preferred embodiments of the present invention, as herein disclosed,are taken as some embodiments for explaining the present invention. Itis to be understood that the present invention should not be restrictedby these embodiments and any modifications and additions are possible sofar as they are not beyond the technical idea or principle based ondescriptions of the scope of the patent claims.

INDUSTRIAL APPLICABILITY

In a gear product having a plurality of tooth formed at a predeterminedpitch on an outer peripheral surface of a disc-form body thereof and amethod for manufacturing the same, by forming a crowning at least at oneend part of a tooth surface of at least one of gears engaging eachother, it is able to reduce the trouble of process for forming acrowning, to abbreviate machining time, to reduce the dispersion ofaccuracy due to abrasion of tools and the wastage cost of tools, toenhance efficiency greatly, and to lower costs.

1. A gear product having a plurality of tooth formed at a predeterminedpitch on an outer peripheral surface of a disc-form body thereof,wherein a crowning is formed at least at one end part of a tooth surfaceof at least one of gears engaging each other.
 2. A gear productaccording to claim 1, wherein said crowning is formed at least at oneend part of an upper side tooth surface or a lower side tooth surface ofat least one or the other gear.
 3. A gear product according to claim 1,wherein said crowning is formed at two end parts arbitrarily selectedfrom four end parts of both of an upper side tooth surface and a lowerside tooth surface of one or the other gear.
 4. A gear product accordingto claim 1, wherein said crowning is formed at three end partsarbitrarily selected from four end parts of both of an upper side toothsurface and a lower side tooth surface of one or the other gear.
 5. Agear product according to claim 1, wherein said crowning is formed at anupper end part of an upper side tooth surface of one gear and saidcrowning is formed at said upper end part and a lower end part of saidupper side tooth surface and a lower end part of a lower side toothsurface of the other gear.
 6. A gear product according to claim 1,wherein said crowning is formed at upper and lower end parts of an upperside tooth surface and an upper end part of a lower side tooth surfaceof one gear, and said crowning is formed at said upper and lower endparts of said upper side tooth surface and a lower end part of saidlower side tooth surface of the other gear.
 7. A gear product accordingto claim 1, wherein said crowning is formed at an upper end part of anupper side tooth surface and a lower end part of a lower side toothsurface of one gear.
 8. A gear product according to claim 1, whereinsaid crowning is formed at upper and lower end parts of an upper sidetooth surface and a lower end part of a lower side tooth surface of onegear and said crowning is formed at said upper end part of said upperside tooth surface and said lower end part of said lower side toothsurface of the other gear.
 9. A gear product according to claim 1,wherein said crowning is formed at a lower end part of an upper sidetooth surface and an upper end part of a lower side tooth surface of onegear.
 10. A gear product according to claim 1, wherein said crowning isformed at a lower end part of an upper side tooth surface and an upperend part of a lower side tooth surface of one gear and said crowning isformed at said lower end part of said upper side tooth surface and saidupper end part of said lower side tooth surface of the other gear.
 11. Agear product having a plurality of tooth formed at a predetermined pitchon an outer peripheral surface of a disc-form body thereof, whereintooth forms of all teeth are unified to one pattern selected from aplurality of pattern in which a crowning is formed at at least one offour parts of every both ends on each tooth surface of said teeth andsaid crowning is not formed at the other of said four parts thereof. 12.A gear product according to claim 11, wherein said selected pattern isone of fourteen patterns comprising four patterns in which said crowningis formed at one of an upper end part or lower end part of an upperinclined surface, and an upper end part or a lower end part of a lowerinclined surface, six patterns in which said crownings are formed at twoparts such as said upper end part and said lower end part of said upperinclined surface, said upper end part of said upper inclined surface andsaid upper end part of said lower inclined surface, said upper end partof said upper inclined surface and said lower end part of said lowerinclined surface, said lower end part of said upper inclined surface andsaid upper end part of said lower inclined surface, said lower end partof said upper inclined surface and said lower end part of said lowerinclined surface, or said upper end part and lower end part of saidlower inclined surface, and four patterns in which said crownings areformed at three parts such as said upper end part and said lower endpart of said upper inclined surface and said upper end part of saidlower inclined surface, said upper end part and said lower end part ofsaid upper inclined surface and said lower end part of said lowerinclined surface, said upper end part of said upper inclined surface andsaid upper end part and said lower end part of said lower inclinedsurface, or said lower end part of said upper inclined surface and saidupper end part and said lower end part of said lower inclined surface.13. A gear product according to any one of claims 1-12, wherein saidplurality of tooth formed on said outer peripheral surface of saiddisc-form part thereof is a helical tooth.
 14. A method formanufacturing a gear product having a plurality of tooth formed at apredetermined pitch on an outer peripheral surface of a disc-form bodythereof, wherein a crowning is formed at least at one end part of toothsurface of at least one of gears engaging each other.
 15. A method formanufacturing a gear product according to claim 14, wherein a tooth formhaving said crowning of a tooth formed on said outer peripheral surfaceis formed by cutting.
 16. A method for manufacturing a gear productaccording to claim 14, wherein a tooth form having said crowning of ahelical tooth formed on said outer peripheral surface is formed byupsetting on forging.
 17. A method for manufacturing a gear productaccording to claim 14, wherein a tooth form having said crowning of ahelical tooth formed on said outer peripheral surface is formed byironing on forging.
 18. A method for manufacturing a gear product,wherein a first molding having a plurality of tooth, having no crowning,formed at a predetermined pitch on an outer peripheral surface of adisc-form body thereof is cut so that tooth forms of all teeth may beunified to a pattern selected from a plurality of pattern in which saidcrowning is formed at at least one of four parts of every both ends oneach tooth surface of said teeth and said crowning is not formed at theother of said four parts thereof.
 19. A method for manufacturing a gearproduct, wherein a first molding having a plurality of helical tooth,having no crowning, formed at a predetermined pitch on an outerperipheral surface of a disc-form body thereof is molded by upsetting sothat said crowning can be formed at an upper part of an upper side toothsurface and a lower part of a lower side tooth surface among four partsof both ends parts of tooth surfaces of said all teeth.
 20. A method formanufacturing a gear product, wherein a first molding having a pluralityof helical tooth, having no crowning, formed at a predetermined pitch onan outer peripheral surface of a disc-form body thereof is molded byironing so that said crowning may be formed at a lower part of an upperside tooth surface and an upper part of a lower side tooth surface amongfour parts of both end parts of tooth surfaces of said all teeth.